我已经将许多活动转换为片段，除了一个之外，一切正常。它在setOnItemClickListener上给出Null Pointer Exception。我检查了很多类似的问题，但无法弄清楚问题。如果任何人都可以提供正确的代码解释问题。
问题在于调试器给出的这一行：
lv.setOnItemClickListener(new OnItemClickListener() {
以下是代码：
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.GradientDrawable;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import java.io.InputStreamReader;
import java.net.URL;
import java.io.BufferedReader;
import java.net.URLConnection;
import android.support.v4.app.Fragment;
public class listtojson extends Fragment {
private ProgressDialog pDialog;
public static String url = "http://www.newsvoice.in/upload_audio_sawdhan/listnews.php";
// JSON Node names
private static final String TAG_CONTACTS = "contacts";
private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";
private static final String TAG_SIZE = "size";
private static final String TAG_PHONE_URL = "url";
private static final String TAG_FILETYPE = "filetype";
private static final String TAG_FILETYPETXT = "filetypetxt";
private static final String TAG_DETAILS = "details";
private static final String TAG_FILEPATH = "filepath";
private static final String TAG_LOCATION = "location";
private static final String TAG_DATETIME = "datetime";
private static final String TAG_USERNAME = "username";
private static final String TAG_HIGHALERT= "highalert";
public int ssid ;
// contacts JSONArray
JSONArray contacts = null;
public TextView view1;
ListView lv;
// Hashmap for ListView
ArrayList<HashMap<String, String>> contactList;
RelativeLayout llLayout;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
FragmentActivity faActivity = (FragmentActivity) super.getActivity();
llLayout = (RelativeLayout) inflater.inflate(R.layout.listnewsjson, container, false);
contactList = new ArrayList<HashMap<String, String>>();
lv = (ListView) llLayout.findViewById(R.id.list); //getListView();
// ListView lv = getActivity().getListView();
// Listview on item click listener
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
String name = ((TextView) view.findViewById(R.id.name))
.getText().toString();
String size = ((TextView) view.findViewById(R.id.size))
.getText().toString();
String description = ((TextView) view.findViewById(R.id.url))
.getText().toString();
String details = ((TextView) view.findViewById(R.id.details))
.getText().toString();
String location = ((TextView) view.findViewById(R.id.location))
.getText().toString();
String datetime = ((TextView) view.findViewById(R.id.datetime))
.getText().toString();
String filetype = ((TextView) view.findViewById(R.id.filetypetxt))
.getText().toString();
String username = ((TextView) view.findViewById(R.id.username))
.getText().toString();
Intent in = new Intent(getActivity().getApplicationContext(), jsondetailActivity.class);
// passing sqlite row id
//= in.putExtra(TAG_ID, sqlite_id);
in.putExtra(TAG_ID, String.valueOf(id));
in.putExtra(TAG_NAME, name);
in.putExtra(TAG_DETAILS, details);
in.putExtra(TAG_LOCATION, location);
in.putExtra(TAG_DATETIME, datetime);
in.putExtra(TAG_FILETYPE, filetype);
in.putExtra(TAG_PHONE_URL, description);
in.putExtra(TAG_SIZE, size);
in.putExtra(TAG_USERNAME, username);
startActivity(in);
}
});
// Calling async task to get json
new GetContacts().execute();
return llLayout;
}
/**
* Async task class to get json by making HTTP call
* */
private class GetContacts extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Loading People News");
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
try {
// Making a request to url and getting response
// String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);
URL requestUrl = new URL(url);
Log.e("Debug", " Sapp 1 : " + requestUrl.toString());
URLConnection con = requestUrl.openConnection();
BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
StringBuilder sb=new StringBuilder();
//Reader rd=new Readable(in);
int cp;
try {
while((cp=in.read())!=-1){
sb.append((char)cp);
}}
catch(Exception e){
}
String jsonStr=sb.toString();
Log.e("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
contacts = jsonObj.getJSONArray(TAG_CONTACTS);
// looping through All Contacts
for (int i = 0; i < contacts.length(); i++) {
JSONObject c = contacts.getJSONObject(i);
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String size = c.getString(TAG_SIZE);
String url = c.getString(TAG_PHONE_URL);
String details = c.getString(TAG_DETAILS);
String location = c.getString(TAG_LOCATION);
String datetime = c.getString(TAG_DATETIME);
String filetype = c.getString(TAG_FILETYPE);
String username = c.getString(TAG_USERNAME);
String highalert = c.getString(TAG_HIGHALERT);
HashMap<String, String> contact = new HashMap<String, String>();
// adding each child node to HashMap key => value
contact.put(TAG_ID, id);
contact.put(TAG_NAME, name);
contact.put(TAG_SIZE, size);
contact.put(TAG_PHONE_URL, url);
contact.put(TAG_DETAILS, details);
contact.put(TAG_LOCATION, location);
contact.put(TAG_DATETIME, datetime);
contact.put(TAG_FILETYPE, filetype);
contact.put(TAG_FILETYPETXT, filetype);
contact.put(TAG_USERNAME, username);
contact.put(TAG_HIGHALERT, highalert);
// adding contact to contact list
contactList.add(contact);
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
}catch(Exception ec){
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
getActivity(), contactList,
R.layout.list_selector, new String[] { TAG_NAME, TAG_SIZE,
TAG_PHONE_URL,TAG_FILETYPE, TAG_FILETYPETXT,TAG_DETAILS,TAG_LOCATION,TAG_DATETIME, TAG_USERNAME, TAG_HIGHALERT}, new int[] { R.id.name,
R.id.size, R.id.url, R.id.filetype,R.id.filetypetxt, R.id.details, R.id.location, R.id.datetime, R.id.username, R.id.highalert });
Log.e("Debug", " Sapp 10"+TAG_NAME);
SimpleAdapter.ViewBinder viewBinder = new SimpleAdapter.ViewBinder() {
@Override
public boolean setViewValue(View view, Object data,
String textRepresentation) {
if (view.getId() == R.id.name) {
((TextView) view).setText((String) data);
return true;
} else if (view.getId() == R.id.size) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.url) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.details) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.location) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.datetime) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.filetypetxt) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.username) {
((TextView) view).setText((String) data);
} else if (view.getId() == R.id.highalert) {
GradientDrawable gd = new GradientDrawable();
gd.setColor(0xffff0000); // Changes this drawbale to use a single color instead of a gradient
gd.setCornerRadius(0);
gd.setSize(10,20);
// view.findViewById(R.id.name).setBackgroundDrawable(gd);
String halert=(String.valueOf((String) data));
if(halert.equals("1")) {
((TextView) view).setText(" ");
((TextView) view).setBackgroundDrawable(gd);
return true;
}
else { return true; }
} else if (view.getId() == R.id.filetype) {
// (view1 = (TextView) findViewById(R.id.filetypetxt)).setText((String) data);
Resources res =getResources();
String tnew=(String.valueOf((String) data));
String tst=tnew;
int sidd=0;
// Log.e("Debug", " Sapp 7:"+(String)data+":");
if(tst.equals("c")) { ssid = R.drawable.ca; }
else if(tst.equals("d")) { ssid = R.drawable.da; }
else if(tst.equals("e")) { ssid = R.drawable.ea; }
// Log.e("Debug", " Sapp 8 :"+ssid+":");
Bitmap bmp = BitmapFactory.decodeResource(res, ssid);
BitmapDrawable ob = new BitmapDrawable(getResources(), bmp);
((ImageView) view).setImageDrawable(ob);
((ImageView) view).setImageBitmap(bmp);
return true;
}
return false;
}
};
((SimpleAdapter) adapter).setViewBinder(viewBinder);
lv.setAdapter(adapter);
registerForContextMenu(lv);
}
}
public static String getFileSize(long size) {
if (size <= 0)
return "0";
final String[] units = new String[] { "B", "KB", "MB", "GB", "TB" };
int digitGroups = (int) (Math.log10(size) / Math.log10(1024));
return new DecimalFormat("#,##0.#").format(size / Math.pow(1024, digitGroups)) + " " + units[digitGroups];
}
}
这是Logcat：
10-14 00:46:53.900 18286-18286/com.sjssoft.sawdhan E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.sjssoft.sawdhan, PID: 18286
java.lang.NullPointerException
at com.sjssoft.sawdhan.listtojson.onCreateView(listtojson.java:87)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1789)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:955)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:740)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1501)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:490)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1072)
at android.support.v4.view.ViewPager.populate(ViewPager.java:918)
at android.support.v4.view.ViewPager$3.run(ViewPager.java:248)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
at android.view.Choreographer.doCallbacks(Choreographer.java:574)
at android.view.Choreographer.doFrame(Choreographer.java:543)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5052)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
at dalvik.system.NativeStart.main(Native Method)
这是XML
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<!-- Main ListView
Always give id value as list(@android:id/list)
-->
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:divider="#b5b5b5"
android:dividerHeight="1dp"
android:listSelector="@drawable/list_selector"
/>
</RelativeLayout>
答案 0 :(得分：0)
@android：id / list使用Android包中的ID“list”，因此您需要在Java代码中将其作为findViewById（android.R.id.list）引用。
答案 1 :(得分：0)
试试这个：
View fragment = inflater.inflate(R.layout.your_fragment_layout, container, false);
lv = (ListView) fragment.findViewById(android.R.id.list);
答案 2 :(得分：0)
你的ArrayList必须是这样的：
ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>
而不是：
llLayout = (RelativeLayout) inflater.inflate(R.layout.listnewsjson, container, false);
插入：
View v = inflater.inflate(R.layout.listnewsjson, container, false);
lv = (ListView) v.findViewById(android.R.id.list);
...
new GetContacts().execute();
return v;
你的AsyncTask必须是这样的：
AsyncTask<Void, Void, ArrayList<HashMap<String, String>>
你的doInBackground必须是这样的：
ArrayList<HashMap<String, String>> doInBackground(Void... params)
你的onPostExecute必须是这样的：
onPostExecute(ArrayList<HashMap<String, String>> result)
设置适配器：
lv.setAdapter(new SomeAdapter(getActivity().getApplicationContext(), result));
...